The present invention relates to a light source device, and more particularly an improvement of a light source especially adapted for use in a photocopying machine in which an object which is spaced apart from the light source by a relatively long distance must be illuminated with uniform intensity in the longitudinal direction of the object.
In general the conventional light sources for the purpose described above comprise a lamp tube made of quartz, Vycor or any other suitable heat-resistant glass, a coiled tungsten filament assembly enclosed in the tube and consisting of alternate light emitting coil sections and non-light-emitting coil sections so as to illuminate an object with uniform intensity, the object being spaced apart from the coiled filament assembly by a predetermined distance, and an inert gas such as argon and halogen or compounds thereof sealed in the lamp tube. In order to provide the non-light-emitting coil sections, a metal bar is placed in the coil assembly so as to short-circuit a desired number of coil turns. Alternatively, a section of coils is attached to the desired number of coils of the filament assembly or a plurality of light emitting coil sections and a plurality of non-light-emitting coils sections are alternately connected into a length of a coiled filament assembly. Therefore the fabrication is complex and involves a relatively large number of steps, and the cost is expensive. In addition, the light source device has a relatively long length so that the weight of the filament assembly enclosed in the lamp tube is considerably heavy. As a result, during the shipment or transportation and handling and operation when the light source device is mounted on a device, the coiled filament assembly tends to be displaced out of its supporting means, to be deformed and to be disconnected and broken of coiled filament due to vibrations. That is, the conventional light source devices have unsatisfactory mechanical strength.